By Bob Goemans
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Manufactured by: Korallin

A product review by Bob Goemans

Korallin Kalkreaktor:

(Written in 2003)

For those of us that maintain reef aquariums, those not equipped with a calcium reactor usually require more husbandry skills in the area of alkalinity and calcium control. Calcification rates by stony corals, coralline algae growth, precipitation of calcium and magnesium/calcium clogged powerheads and/or the demand on system carbonates and bicarbonates to maintain pH and alkalinity put a severe drain on these seawater elements. This greatly adds to the time needed to properly maintain the reef aquarium. For those of us that have learned of calcium reactor benefits, we now sit back and have time for the spouse again so to speak. At least, that's how my wife described it, however not exactly in those words!

Reactors in general fall into a category of highly specialized equipment. There are those that add dissolved oxygen, control carbon dioxide/pH levels, or those such as calcium reactors which supplement/control alkalinity/calcium levels. Reactors are useful for those hobbyists who want to maximize certain aspects of their marine environment. However, in the wrong hands, they can quickly get out of control and ruin a perfectly good aquarium. If there is a parameter that could be enhanced with a particular reactor, it may be a good idea to ask someone, especially someone that is not selling the device, if it's something you really need. Yet, where the reef hobbyist is concerned, I doubt whether there's a system that wouldn't benefit from a calcium reactor.

As for calcium reactors, they are filled with a calcareous material such as crushed coral, oyster shell, or aragonite. A small amount of carbon dioxide (CO2), supplied by a compressed CO2 cylinder, is mixed with incoming water from the aquarium. The pH reduced/acidified water, near 6.0, is then circulated throughout the reactors calcium carbonate media, slowly dissolving it and thereby releasing small amounts of calcium, various carbonates and bicarbonates along with some trace elements. The water in the reactor experiences a rise in dKH, and is slowly returned/dripped back into the aquarium. Calcium reactors also come with a device called a bubble counter, which is nothing more than a clear cylinder filled with water in which you can see/control the flow rate of CO2 bubbles entering the reactor.

Okay, you're now thinking about how much time/cost/hassle would be saved if you no longer had to prepare and add Kalkwasser, and/or dose other types of calcium/buffer additives. You might even get to know your spouse again! Imagine having a very stable reef aquarium environment where calcium level remains in the 400's, and alkalinity is easily maintained between 12 to 14 dKH! Just imagine your supply of additives reduced to only iodine! Well, that's very possible if you have a calcium reactor connected to your aquarium.

Monolith Marine Monsters asked me to test their new, 'second generation' KORALLIN C-1500 Kalkreaktor. I say 'second generation' because this new improved version has corrected some bothersome design issues in the initial version. I'll explain more about these improvements further on in this article.

Let me begin by saying the clear acrylic cylinder-shaped KORALLIN Kalkreaktor is a quality made unit. It comes in two sizes: a C-1500 model rated to handle a 400 gallon reef system; and, their C-3000 unit, rated to handle a 750 gallon system. The C-1500 unit stands 15.75 inches tall including the top mounted Eheim pump and its connecting piping. It holds 6.6 pounds (3 kg) of media. The C-3000 is 30.0 inches tall, holds 14.3 pounds of media and has the same footprint as the smaller unit.

The KORALLIN unit has many features not found on other calcium reactors. The first of which, is its extremely small footprint, a six inch diameter! Second is its extremely sturdy construction. Another feature is that its Eheim pump is top mounted so as to stop excessive CO2 from entering the aquarium. And, its Eheim pump consumes only five watts of electrical energy on the C-1500 unit and ten watts on the C-3000 unit, besides being totally quiet when operating! If that wasn't good enough, CO2 usage is extremely low because it's drawn into the Eheim's impeller where it's reduced into millions of micro-sized bubbles and mixed with the circulating water inside the unit. This unique aspirating-venturi feature provides for very efficient use of the CO2 gas and reduces the needed flow to approximately 10 bubbles a minute! Yes, I said ten bubbles a minute, not one to two bubbles per second as in some other reactors!

During the initial installation/operation of the unit, there may be some trapped air in the units pump, inlet tubing or in the media itself. It may finally manifest itself as an air space at the inside top of the reaction cylinder. However, there's a ventilation valve located in the top of the unit that can be opened, so as to bleed-off the accumulating air.

As mentioned above, the Eheim is located on the top of the reactor cylinder. If an excessive amount of CO2 gas is applied and creates a large enough air pocket at the top inside of the unit, the gas would flow into the internal inlet of the pump, which extends downward about one inch from the top of the reactor, and halt circulation of water within the unit. If this happens, the pump has now become air bound and even though it's still running, it's not drawing water from the aquarium or returning any effluent. If the Eheim pump runs dry, there is an overheat switch that will stop the pump, as well as producing an audible tone to notify the hobbyist it requires attention. Opening the ventilation valve, a quality made ball valve, will bleed-off the excess CO2. However, the speed of the CO2 bubbles needs further tweaking so it will not continue to occur. Once the flow of CO2 bubbles are correctly regulated, somewhere between 10 - 12 bubbles per minute, no further air pockets should occur.

The demo model, a C-1500 unit, its Eheim pump and bubble counter arrived my doorstep via the brown gorilla covered in bubble-wrap inside a small cardboard box. The unit is so well made that it could have been shipped without any protective covering! However, the written instructions for loading the unit with media and adjusting its flow need further revision. Revised instructions will soon be available. When I first looked at the unit, I thought, "how strange, it loads from the bottom, and that could easily clog its top input to the pump." I called Edward Tsang with Monolith Marine Monsters and asked if there was anyone with previous experience with the unit. He recommended I call Gianni Angelidi with Tropico Reeflife in Florida. Gianni was kind enough to describe the earlier unit and we compared it to this second generation model. Instead of iron bolts in the removable O-ring fitted base, the new unit had stainless steel bolts. Also, all tubing fittings, i.e., effluent, inlet, and CO2 inlet were now leak-proof nylon compression fittings. Big improvements I must say!

Gianni suggested placing a powerhead strainer, over the Eheim's internal inlet tube. I removed the bottom plate of the unit, placed a screen from an old powerhead over the Eheim's inlet tube and filled the unit to the prescribed depth with the supplied KORALlith media, a phosphate free calcium carbonate product having a grain size of about 4 - 5 mm. The base plate and O-ring were reinstalled and it was time to install the Eheim pump, which took all of ten seconds! Its inlet and outlet connections simply slip into corresponding vinyl tubes already on the reactors top surface. A small nylon screw firmly secures the Eheim's base plate to the top of the reactor. The inputs to the Eheim come from three sources: CO2, water from inside the reactor, and that coming from the aquarium. It has one output connection that delivers conditioned water back to the aquarium. The Eheim continues to circulate these two sources of water and CO2 in the unit. Water is withdrawn from underneath a small felt covered plenum at the bottom of the unit by a long tube extending from the pump to just below the plenum, thereby providing a well mixed effluent high in dKH/calcium and very low in CO2 for return to the aquarium.

Next, the bubble counter was mounted near the reactor and connected to the Eheim and its supply of CO2. Through one of the still open connections (the effluent fitting), the unit was filled with aquarium water. I used a small powerhead with a length of airline tubing to fill the unit while leaving the ventilation valve open to bleed-off air inside the unit. When the reactor was full, including the Eheim pump, I inserted the effluent tube, tightened its fitting and closed the ventilation valve. All tubing for hooking up the effluent, feed line and CO2 supply lines is regular airline tubing, and it works well! In fact, it is recommended that silicone tubing not be used. KORALLIN say's that it has been proven there is a certain chemical reaction between carbon dioxide and silicone tubing that makes the reactor less efficient. Another feature is that there are no unsightly PVC piping or fittings! I started the pump and adjusted the effluent rate to 40 drops per minute and the CO2 bubble rate to 10 bubbles per minute. In twelve hours I had an effluent that was 15.5 meq/l, or 45 dKH! Keep in mind the effluent should enter the aquarium/sump a little above its surface so you can count the returning drops. There's another small quality-made ball valve that comes with the unit for placement in the effluent tubing so you can control its flow. All in all, it's an extremely small, totally quite and efficient, both energy-wise and effluent-wise, unit and it did not have any leaks.

Before I close this review of the KORALLIN Kalkreaktor, I want to note that it doesn't come with a CO2 bottle or regulator. These are something you will need to supply and there is some thought on this subject matter that you should be aware of before you purchase this type equipment. First, I highly recommend you purchase your CO2 bottle from a local welding supply company. Bottles come in different size, i.e., 5, 10, 15, 20 pound and larger. But, since you are going to refill the bottle at some point in time, your local welding company may not want to refill a bottle they have no safety record on. For safety reasons and your convenience, I recommend you procure your bottle from a local welding company. Next, it would be more practical to purchase a regulator that is equipped with a "solenoid." For those of you that are not familiar with that term, it is simply an electrical device that will shut off the gas flow when there is a power failure. If you purchase a regulator without a solenoid, CO2 will continue to flow during a power outage, possibly evacuating the reactor water and then finding its way to your aquarium, introducing a large dose of CO2 into the aquarium. Purchase a regulator equipped with a 110V solenoid.

As you may know, I've used calcium reactors for the past few years. But with the KORALLIN Kalkreaktor, I'm finding my pH remains slightly higher as no excess CO2 is entering my aquarium, there is no heat or noise associated with the Eheim pump, and energy consumption is extremely low. Add to that its extremely small footprint and it makes for a unit that is probably impossible to beat in features and price. However, I've had to increase effluent rate to about 70 drops per minute to keep pace with the alkalinity/calcium draw in my 125 gallon reef aquarium. This has reduced effluent dKH to about 9 meq/l, but seems to be working quite well. For that reason, I'm unsure if the C-1500 would adequately handle a 400 gallon reef system where there were many sps corals and significant coralline algae growth. Also, loading from the bottom doesn't make sense and this aspect of the unit should be changed in future production models. Okay, what is the unit's price. The C-1500 sells for $375, and the C-3000 sells for $550. To refill the C-1500, the KORALlith media costs $24.

Of course, you may like adding calcium and buffer to your aquarium or having a closet full of additives! You may also like cleaning powerheads of calcium buildup every six months! If that's the case, don't checkout the KORALLIN Kalkreaktor! However, if the spouse is demanding more attention, contact Monolith Marine Monsters for further information.

Monolith Marine Monsters at Four Canal Park, Suite 508, Cambridge, MA 02141, phone (617) 494-8396, fax (617) 494-8396,

Tropico Reeflife, Attention Gianni Angelidi, (813) 942-3008, Fax (813) 937-3088

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